MySQL 5.7服务无法终止问题求助

问题现状 #

安装MySQL 5.7后，3306端口存在活跃服务，但执行service mysql stop、service mysqld stop均无法终止；系统中未找到活跃的MySQL进程，但service mysql status显示服务启动失败，且systemd一直在自动重启服务。

相关命令输出 #

service mysql status输出：

● mysql.service - MySQL Community Server
     Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Wed 2022-11-16 10:09:46 CET; 9min ago
    Process: 65951 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
    Process: 65990 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid (code=exited, status=1/FAILURE)

Nov 16 10:09:44 user systemd[1]: Starting MySQL Community Server...
Nov 16 10:09:44 user mysqld[65990]: Initialization of mysqld failed: 0
Nov 16 10:09:44 user systemd[1]: mysql.service: Control process exited, code=exited, status=1/FAILURE
Nov 16 10:09:46 user systemd[1]: mysql.service: Failed with result 'exit-code'.
Nov 16 10:09:46 user systemd[1]: Stopped MySQL Community Server.

journalctl -xe关键输出：

-- Subject: A start job for unit mysql.service has failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- A start job for unit mysql.service has finished with a failure.
-- 
-- The job identifier is 13189 and the job result is failed.
Nov 16 10:36:40 user systemd[1]: mysql.service: Scheduled restart job, restart counter is at 37.
-- Subject: Automatic restarting of a unit has been scheduled
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- Automatic restarting of the unit mysql.service has been scheduled, as the result for
-- the configured Restart= setting for the unit.
Nov 16 10:36:40 user mysqld[71662]: Initialization of mysqld failed: 0
Nov 16 10:36:40 user systemd[1]: mysql.service: Control process exited, code=exited, status=1/FAILURE

解决步骤 #

1. 彻底停止systemd的自动重启机制 #

systemd默认会自动重启失败的服务，先彻底禁用该行为并停止服务：

sudo systemctl stop mysql.service
sudo systemctl disable mysql.service
sudo systemctl mask mysql.service

mask命令会将服务链接到/dev/null，彻底阻止服务被意外启动。

2. 排查3306端口占用情况 #

用以下命令精准定位端口占用进程：

# 方法1：用lsof查看
sudo lsof -i :3306
# 方法2：用netstat查看
sudo netstat -tulpn | grep 3306
# 方法3：用ss查看（更高效）
sudo ss -tulpn | grep 3306

• 如果找到对应进程，用sudo kill -9 <PID>强制终止
• 如果未找到进程，可能是TCP套接字残留，可重启网络服务：sudo systemctl restart networking

3. 排查MySQL初始化失败原因 #

查看MySQL错误日志，获取初始化失败的具体信息：

sudo cat /var/log/mysql/error.log

常见失败原因及修复：

• 权限问题：/var/lib/mysql目录权限错误，执行以下命令修复：

  sudo chown -R mysql:mysql /var/lib/mysql
  sudo chmod -R 755 /var/lib/mysql
  

• 配置文件错误：检查/etc/mysql/my.cnf或/etc/mysql/mysql.conf.d/mysqld.cnf中的配置项，比如datadir路径是否正确、端口是否冲突等。
• 磁盘空间不足：用df -h检查磁盘剩余空间，清理冗余文件释放空间。

4. 重新初始化MySQL（仅在数据可备份或无重要数据时操作） #

如果初始化问题无法修复，可尝试重新初始化：

# 先备份数据目录
sudo cp -r /var/lib/mysql /var/lib/mysql_backup
# 停止服务（确保已停止）
sudo systemctl stop mysql.service
# 重新初始化
sudo mysqld --initialize --user=mysql
# 启动服务
sudo systemctl unmask mysql.service
sudo systemctl enable mysql.service
sudo systemctl start mysql.service

初始化完成后，可在错误日志中找到初始root密码：sudo grep 'temporary password' /var/log/mysql/error.log

内容的提问来源于stack exchange，提问作者jacksc0tt